1. Field of the Invention
The present invention relates to a process for the preparation of a copper phthalocyanine pigment having the .beta. form alone or one having both .alpha. and .beta. forms mixedly. More particularly, it relates to a process for the preparation of a copper phthalocyanine pigment having the .beta. form alone or one having both .alpha. and .beta. forms mixedly, which comprises dry grinding crude copper phthalocyanine and dipping or wet grinding the thus obtained dry ground copper phthalocyanine in an aqueous solution of a mineral acid.
2. Description of the Prior Art
Crude copper phthalocyanine prepared by the synthesis in an organic solvent according to the prior art is composed of coarse primary particles, so that it exhibits poor clarity and poor color strength when dispersed in various vehicles, thus being lowly valuable as a colorant. Accordingly, such crude copper phthalocyanine must be divided more finely prior to the application thereof to various fields.
When crude copper phthalocyanine as described above is ground in a ball mill or vibrating mill, it is gradually converted into amorphous one. Further, as the grinding thereof proceeds, the grinding agglomeration becomes more intensive, so that the resulting ground copper phthalocyanine exhibits only very low color strength when dispersed in a vehicle, owing to the high agglomerating power thereof. As a process for preparing the .beta.-type pigment, for example, Japanese Patent Application Laid-Open No. (sho.) 52-69435 discloses a process of treating crude copper phthalocyanine exhibiting intensive grinding agglomeration in a crystallizing solvent such as xylene or an aqueous emulsion thereof to carry out the pigmentation through crystal transformation. However, this process has a disadvantage in that when ground crude copper phthalocyanine is dipped in a crystallizing solvent or an aqueous emulsion thereof, the particles thereof cause excessive crystal growth to result in coarse particles again.
As a wet grinding process for preparing the .beta.-type pigment, a process of grinding crude copper phthalocyanine with a kneader or a mixer in the presence of a polyol (a conditioning medium) has been known. However, this process is also disadvantageous in that the grinding takes a long time to result in enhanced power consumption. Thereafter, although various improved processes, for example,
(a) process of adding ferric chloride (Japanese Patent Application Laid-Open No. (sho.) 51-134722). PA0 (b) process of adding an alkali hydroxide (Japanese Patent Application Laid-Open No. (sho.) 51-69524) and PA0 (c) process of adding calcium chloride as a viscosity stabilizer together with a grinding aid such as sodium chloride or sodium sulfate (Japanese Patent Application Laid-Open No. (sho.) 51-11138) have been disclosed, PA0 (1) the process gives a pigment which is composed of fine particles and has a large specific surface area, a high color strength and a high clarity, PA0 (2) the process of the present invention uses an inexpensive mineral acid which is suitable for massuse, thus being economical, PA0 (3) the process of the present invention need not use any organic solvent, so that it permits the simplification of waste water disposal and is advantageous in respects of fire prevention and workability, though the preparation of a copper phthalocyanine pigment having the .beta. form according to the prior art necessitates an organic solvent, PA0 (4) the size and shape of the pigment particle can be widely varied by changing the acid concentration and the treatment time, PA0 (5) the content ratio of the .alpha. form to the .beta. form can be arbitrarily varied by changing the .alpha. form content of the crude copper phthalocyanine at dry grinding, acid concentration and treatment temperature. Thereby, the hue of the resulting pigment can be widely adjusted in a range of from greenish blue (the color of the .beta. form) to reddish blue (the color of the .alpha. form). Thus, the process of the present invention is highly valuable as a process for preparing the pigment on an industrial scale.
they also cause troubles in a grinding or washing step or have a disadvantage that it is difficult to prepare a high-quality pigment.
Meanwhile, as a process for preparing the .alpha.-type pigment, pigmentation processes using sulfuric acid which is one of mineral acids have been known. That is, an acid pasting process of treating crude copper phthalocyanine in a state dissolved in a large amount of concentrated sulfuric acid and an acid slurry process of treating crude copper phthalocyanine with a large amount of sulfuric acid having a concentration insufficient for dissolving the pigment to form a sulfate are disclosed in U.S. Pat. Nos. 3,024,247, 2,770,629 and 2,334,812.
Further, Japanese Patent Application Laid-Open No. (hei.) 1-70568 discloses a process which comprises adding dry ground crude copper phthalocyanine which is intensively agglomerative to a 50 to 90% by weight aqueous solution of sulfuric acid to form a slurry of a sulfate thereof in the presence of a crystal growth inhibitor, adding water to this slurry to form a precipitate and thereby obtaining a pigment grade copper phthalocyanine. However, the application of this process is limited to the preparation of copper phthalocyanine having the .alpha. form.
Furthermore, Japanese Patent Application Laid-Open No. (sho.) 58-104960 discloses a process which comprises forming a slurry of dry ground chlorinated crude copper phthalocyanine containing 3 to 5% by weight of chlorine in a 50 to 60% by weight aqueous solution of sulfuric acid and pouring this slurry into water to obtain a copper phthalocyanine pigment. However, the pigments obtained by this process are also limited to copper phthalocyanine pigments each having the .alpha. form.
Although Japanese Patent Application Laid-Open No. (sho.) 60-31344 discloses a process which comprises dry grinding crude copper phthalocyanine together with a non-oxidizing acid and mixing the thus obtained pigment derivative with an organic solvent such as diethylene glycol, this process is disadvantageous in that the pigment particles cause excessive crystal growth in the presence of the solvent and that the solvent must be recovered.